Electronic equipment systems employ clock sources to control the timing of logic components within the systems. In traditional systems, a clock generation module or card is employed on the backplane of the system to distribute one or several clocks through the backplane to each chassis card. The clock generation module may include an oscillator crystal driving a phase-locked loop. The clock generation module may also possess various filtering circuits and clock duplication functionality.
The traditional approach created a single point of failure for the supported system. Specifically, if the clock module malfunctioned for any reason, the entire system would cease to function. Accordingly, redundant clock generation designs have been implemented. In one example, a clock generation module includes two oscillator crystals. During ordinary operation, one of the oscillator crystals is used as a master device to generate the clock for distribution and the other oscillator operates in synchronization. If the master oscillator fails for any reason, circuitry within the clock module detects the failure and switches the clock generation to the timing signal generated by the secondary oscillator.